1. Field of the Invention
This invention relates to a seat reclining apparatus having a pawl and a ratchet.
2. Description of the Prior Art
As shown in FIG. 5, a seat used in an automotive vehicle has a lower arm 1 on both sides of a seat for supporting a seat cushion (not shown), and an upper arm 2 on both sides of the seat for supporting a seat back (not shown). A reclining apparatus 3 is mounted on both ends of a connecting rod 4 that connects the arms 1, 2 on both sides of the seat.
Each reclining apparatus 3 has at least a ratchet 5 secured to the lower portion of the corresponding upper arm 2, a release lever 7 supported on the connecting rod 4 and acted upon by the biasing force of a spring 6, and a pawl 8 pivoted on the corresponding lower arm 1 so as to be free to engage the ratchet 5. The reclining apparatus 3 is provided on each side of the seat.
In the example of FIG. 5, the release lever 7 is provided with a cam slot 9, a pin 10 fixed to the pawl 8 is mated with the cam slot 9, and a ring 11 pivotally supported on the release lever 7 is brought into sliding contact with a cam surface 12 on the side face of the pawl 8.
When the release lever 7 is lifted, the position of the cam slot 9 moves as the ring 11 moves along the cam surface 12, and the position of the pin 10 is changed owing to the movement of the cam slot 9, whereby the ratchet 5 and the pawl 8 are caused to disengage. As a result, the upper arm 2 is allowed to turn freely relative to the lower arm 1 and may be turned about the connecting rod 4 to any desired attitude. The release lever 7 is then returned to its original position to reengage the ratchet 5 and pawl 8 and establish the fixed relation between the arms 1, 2.
Another arrangement is known in which the cam slot 9 is provided in the pawl 8 and the pin 10 is fixed. In still another known arrangement, the slot 9 and pin 10 are eliminated and the movement of the pawl 8 is made to follow up the operation of the release lever 7 solely by the ring 11.
For the details of such prior-art arrangements of reclining apparatus, refer to the specifications of Japanese Utility Model Publication No. 61-29322 and U.S. Pat. No. 4,660,886.
The arrangement illustrated in FIG. 5 is provided symmetrically on the lower arms on both sides of the seat. The motion of one release lever, which is provided with a handle, is transmitted to the other release lever, which is devoid of a handle, via the connecting rod. Further, it is required that each release lever have a spring for strengthening the engagement between the pawl and ratchet.
In particular, the spring interposed between each lower arm and each release lever takes up the limited amount of space available around the seat and hampers a degree of freedom in terms of seat design.
Furthermore, as will be understood from the illustrated example of the prior art, the motion of the pawl always follows up the motion of the release lever. Accordingly, a lever corresponding to the release lever on one side of the seat is disposed on the other side of the seat, this lever and the pawl on the other side are operatively associated, and it is required that both levers be moved in unison by the connecting rod.
This conventional arrangement is disadvantageous in that width is increased by an amount equivalent to the lever on the other side.